Fast packet technology provides efficiency and resilience for transfer of information for networks containing a diversity of traffic types such as voice, constant bit rate (CBR), video, and multiple types of data traffic from diverse applications. Present communication systems rely on a particular network switching type to transport specific traffic types. For example, circuit switching is most appropriate for voice and other constant bit rate traffic sources. Frame switch technologies (X.25 and frame relay) are most appropriate for bursty data traffic (wide area LAN inter-connect and transaction based applications), but are not appropriate for video or voice traffic.
The spectrum of the more well known switching technologies, listed progressively for fixed bit rate and simplicity to variable bit rate and complexity, are: circuit switching (CS), multirate circuit switching, fast circuit switching, cell relay (CR), fast packet switching (FP), and frame relay (FR) (frame switching).
FP and CR networking technologies are very similar in nature and solve many of the same networking problems. Both allow the construction of efficient and cost effective networks that carry diverse traffic types such as voice, video, CBR, and bursty data traffic. The major common element of FP and CR networks is that both convert (adapt) various types of traffic to a common format before transporting the traffic across the network. In both cases, the common form is a "small packet", where small is typically 64 or less octets. Each packet contains a network header containing destination or logical address, congestion level information, priority information, etc., and a payload portion containing the user's data. The main difference between a FP and CR network is that the size of the packet in a CR network is a fixed length, and the size of a packet in a FP network is variable in length.
The efficiency and diversity of CR and FP networks is obtained by the adaption of the traffic source, at the edge of the network, i.e., where the network begins/ends, to a common form or packet. This allows network switches to handle the traffic in a common way inside each type of network independent of the source type. Note that at the edges of the network, different traffic types need to be adapted to the common form, or packets. These adaption procedures are traffic source type dependent. For example, CCITT AAL1 protocol is used for adaption of CBR traffic to ATM (asynchronous transfer mode) cells, and CCITT AAL5 protocol is used for adaption of HDLC framed traffic to ATM cells.
CR and FP networks both allow for efficient networks that carry diverse types of traffic. However, there has been no efficient means of inter-networking between CR and FP networks. The main hindrance is that the adaption procedures used by FP and CR networking technologies are similar, but different. Therefore, the only method of inter-networking has been to adapt the packets of one type packet to the original form, and then adapt the original form to the other packet type. This level of processing at inter-networking points is costly and adds unacceptable transmission delay to the traffic.
As users and devices communicate with one another there develops a need to communicate also across information networking systems that use different types. Thus, there is a need for a fast packet adaptation method that ensures packet portability across diverse switching type networks.